Faculty of Engineering

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Author: search.filters.author.Rathnayake, U. SSubject: search.filters.subject.NSGA II

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Now showing 1 - 4 of 4
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    PublicationOpen Access
    Optimal control of urban sewer systems under enhanced water quality modeling
    (5th International conference on Sustainable Built Environment, 2014) Rathnayake, U. S
    Agricultural lands usually carry a considerable amount of phosphorous and nitrogen. This is due to the routinely added chemical fertilizers. Phosphorous is identified as a non-point source pollutant that causes eutrophication in surface waters. Even though, phosphorous is less mobile than nitrogen, soil erosion in agricultural lands leads to increase the phosphorous levels in surface water. Therefore, it is always better to consider phosphorous concentration when considering the receiving water quality due to combined sewer overflows (CSOs). Rathnayake and Tanyimboh’s optimal control model for urban sewer systems is capable of assessing water quality in receiving water due to CSOs. However, it only includes the concentrations of total suspended solids (TSS), chemical oxygen demand (COD), nitrates and nitrites (NOX), five-day biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN). Therefore, there is a necessity to improve the water quality analysis in Rathnayake and Tanyimboh’s optimal model. This paper presents an enhanced water quality approach, including phosphorous concentrations, in control of urban sewer networks. The enhanced model is applied to a real world combined sewer network. Results show that the enhanced model produces better approach compared to the existing Rathnayake and Tanyimboh’s control model.
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    PublicationEmbargo
    Review of binary tournament constraint handling technique in NSGA II for optimal control of combined sewer systems
    (Taylor & Francis, 2016-01) Rathnayake, U. S
    Binary tournament constraint handling technique in Non Sorted Genetic Algorithm II (NSGA II) has both advantages and disadvantages. This constraint handling technique is fairly simple; however, it solves the issues in identifying the penalty functions for multi- objective optimization problems. This paper reviews the constraint handling approach in NSGA II and compares it with an alternative constraint handling approach for optimal control of combined sewer systems. Interesting results are presented and it can be concluded that the alternative constraint handling approach produces better results; however, this alternative constraint handling approach has to be used with adequate care.
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    PublicationEmbargo
    Enhanced water quality modelling for optimal control of drainage systems under SWMM constraint handling approach
    (IOS Press, 2015-01-01) Rathnayake, U. S
    Phosphorus and nitrogen are two important nutrients to plants. Therefore, fertilizers usually used in agricultural lands hold a significant amount of phosphorus and nitrogen. Even though these two are essential for plants, they are treated as pollutants when they are contaminated to the fresh waters. Therefore, phosphorus in stormwater runoff is a concerned topic for combined sewer overflows (CSOs). Rathnayake and Tanyimboh's optimal control model was capable of handling five different water quality parameters (chemical oxygen demand, bio-chemical oxygen demand, total suspended solids, total Kjeldhal nitrogen and nitrates and nitrites) in CSOs. However, the enhanced approach is capable of integrating phosphorus concentrations into the analysis of water quality from CSOs. The new optimal control model for drainage systems was run and compared against the previous work by the author. Promising findings are illustrated from the newly developed model in controlling drainage systems.
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    PublicationOpen Access
    Migrating storms and optimal control of urban sewer networks
    (Multidisciplinary Digital Publishing Institute, 2015-12) Rathnayake, U. S
    Uniform storms are generally applied in most of the research on sewer systems. This is for modeling simplicity. However, in the real world, these conditions may not be applicable. It is very important to consider the migration behavior of storms not only in the design of combined sewers, but also in controlling them. Therefore, this research was carried out to improve Rathnayake and Tanyimboh’s optimal control algorithm for migrating storms. Promising results were found from the model improvement. Feasible solutions were obtained from the multi-objective optimization and, in addition, the role of on-line storage tanks was well placed.